Reason #120 • April 30th, 2026

Presenting bytes with ActiveSupport's number_to_human_size

Humans do not think in raw byte counts. At least I do not. ActiveSupport's NumberHelper#number_to_human_size fixes that.

Ruby
include ActiveSupport::NumberHelper

number_to_human_size(1234)
# => "1.21 KB"

number_to_human_size(1_234_567)
# => "1.18 MB"

number_to_human_size(5_242_880)
# => "5 MB"
JavaScript
const numberToHumanSize = (bytes) => {
  const units = ["Bytes", "KB", "MB", "GB", "TB"];
  let value = bytes;
  let index = 0;

  while (value >= 1024 && index < units.length - 1) {
    value /= 1024;
    index += 1;
  }

  return `${parseFloat(value.toPrecision(3))} ${units[index]}`;
};

numberToHumanSize(1234567);
// => "1.18 MB"

This helper pairs beautifully with ActiveSupport's numeric byte helpers like 5.megabytes, which means both the calculation and the presentation can stay readable.

History

number_to_human_size first appeared in Rails 0.12.0, released in 2005, after being moved over from the older TextHelper#human_size.

It joined ActiveSupport::NumberHelper after some refactoring in Rails 4.0.0, released in 2013.

Reason #121 ?